Studies On The Effects Of Pre-harvest Sprouting, Different Drying Methods And Harvest Date On Rice Quality

Moist conditions prevail or untimely rain would result in pre-harvest sprouting(PHS), which seriously affected on rice yield and quality.Different drying conditions and harvest date have also affected on rice quality.Six rice varieties of 351A/ZhiXuan,An-Yu zao1, Zhu-Qing,An-Xuan 6,Japonica rice and late-maturing Japonica 212 were selected as experimental materials,which studied pre-harvest sprouting and different drying treatment and harvest date on quality office.The results were as follows:1 The effect of the pre-harvest sprouting on quality of riceWith the deepening of grain germination depth,the quality of rice decreased gradually. As the deepening depth germination rate,the brown rice rate,the milled rice rate,the head rice rate decreased gradually,moreover,head rice rate was the biggest decline,chalky rice rate and chalkiness size,gelatinization temperature and amylose content gradually increased,the gel consistency and crude protein content decreased gradually.The results showed that there was significant difference in RVA peak viscosity,breakdown,cool viscosity setback and consistency viscosity in the course of intensive germination.The pre-harvest sprouting has serious effect on its eating quality of rice.2 The effect of different drying methods on quality of riceFrom the milling quality,the temperature in the drying oven 50℃venues and cement drying(35～60℃) rate of brown flee,milled rice rate and head rice rate was significantly lower than the rate of land space(20～40℃) and air dry at room temperature(18～22℃), especially,the head rice rate changed significantly,dried by 50℃constant temperature was the lowest,while dried by the room temperature was highest.Drying different way of milled rice rate of the largest,heated drying oven 50℃minimum,the highest dry at room temperature.From the appearance of quality,the chalky rice rate and chalkiness size dried by 50℃constant temperature and cement was significantly higher than that of 35℃constant temperature and room temperature,with the exception of Zhuqing(chalky rice rate of 100%).The chalky rice rate and chalkiness size dried by 50℃temperature was maximum,the minimum of that dried by room temperature.From cooking and nutritional quality,the gelatinization temperature,gelatinization consistency,amylose content and crude protein content dried by 50℃constant temperature was the highest,while that dried by the room temperature was lowest,3 The effect of harvest date on quality of riceAs the harvest date of delay,the brown rice rate,milled rice rate,the rate of head rice and crude protein content of early,middle and late rice gradually increased and then(35d after initial heading in early rice,40d after initial heading in middle and late rice) decreased, chalky rice rate and chalkiness rice and gelatinization temperature was decreased,Alkali consumers value increased,gel consistency became longer,rice glue softened,amylose content increased.Too early or late harvest would affect the quality of rice.RVA profiles of peak viscosity and breakdown were decrease firstly and rise later with pre-harvest date delayed,while,cool viscosity,setback consistence were gradually reduce,then increased, so resulted in the decline in rice eating quality.Therefore,chose suitable harvest date(early rice after heading 30～35d,middle and late rice after heading 35～40d) can improve rice quality.